The Gothic Arch Folly in Belvedere House is quite a structure, built as an art piece to be viewed upon from vantage points in the big house c.1760, and not as you would initially think - that it was ruins of some medieval castle.

"In Georgian times the inclusion of such follies as part of the overall improvements to the landscape were to provide subjects for melancholic contemplation of the triumph of civilisation over barbarity" - Belvedere House website